Experimental Design Important Terms

Observations data that are descriptions of qualities such as shape, color, taste, feel, etc… acquired by using your senses Two Types: Objective observation Subjective observation

2 Types of Observations Objective Subjective an observation based on fact fact – a piece of information that can be strictly defined and proved true. Subjective an observation based on opinion opinion – a statement that expresses a belief, value, or feeling

Objective or Subjective? Science looks like fun today! Subjective Kanye West’s songs sound good! The counter-tops in class are black! Objective School French fries taste good! The summer was too short! There are sixty seconds in a minute!

Objective or Subjective? Which type of observations should be used in science? Objective observations should be used in science because they are based on facts and the basis of science is to identify the facts!

Inference an explanation that tries to make sense of your observations influenced by your experiences/prior knowledge these explanations may not be true Example Observation: John was breathing heavily as he walked into the classroom. Possible Inferences: He ran to class because he was going to be late He just played basketball in gym

What would you infer? Everyone is closing their book because… Many students buy French fries because… Students arrived to class sweaty because… 4. All of the students are laughing because…

Hypothesis a working explanation or trial answer to a problem an “educated guess” can be written in the form of an “If..., then..., because...” statement is not necessarily proven correct just because data/results from one experiment supports it when repeatedly supported by the same results  theories  laws Example If an individual increases his/her activity level, then their heart rate will increase because the body’s muscles (cells) will require more oxygen to function at a higher level. A faster beating heart will increase blood flow; thus, allowing an increased concentration of oxygen to reach the cells in need.

Data factual information Two Types 1. Quantitative 2. Qualitative

2 Types of Data Quantitative data consisting of numbers Qualitative Example Heart rate (80 beats/minute) Qualitative data consisting of verbal descriptions or information gathered using scales without numbers Examples Verbal description of heart rate (fast or slow)

Repeated Trials experimental tests done more than once necessary to provide more accurate results; data is averaged together lessens the impact of a chance error on the experimental results Examples In the heart rates lab each participant recorded their heart rates after performing various activities. Each participant’s data (for resting, walking, and running) represents a trial. If five total individuals performed the activities and gathered data, then there were a total of five trials.

Variables things that can be assigned or take on different values in an experiment any factor that can change Two Types 1. Independent 2. Dependent

Two Types of Variables Independent variables that are purposely changed or manipulated in an experiment the factor that you wish to test usually expressed after the word “if” in the hypothesis could be thought of as the “cause” in a cause and effect relationship Example The activity level (resting, walking, running) Dependent variables that may change as a result of the independent variable the factor you measure to gather results usually expressed after the word “then” in the hypothesis could be thought of as the “effect” in a cause and effect relationship Example The person’s heart rate

Identify the Variables independent variable If a student chooses to not study, then they will earn a poor grade. If you drink Gatorade before a soccer game, then you will score more goals. If you increase the mechanical advantage of a pulley system used to move an object, then the input force becomes less. dependent variable independent variable dependent variable independent variable dependent variable

Control or Control Group a group of subjects in an experiment that are not given any special treatment something that is not manipulated same as the experimental group in every possible way, except for the factor being tested a neutral point of reference for comparison – it allows you to see what changing a variable does by comparing it to not changing anything. Example The resting heart rate represented the baseline heart rate to which any increase in activity level was compared to.

Constants Factors in an experiment (both in the experimental and control groups) that are kept the same and not allowed to change Examples One minute was consistently the amount of time allotted to perform the necessary activity The type of activity performed The stopwatch used during data collection The method used to measure the heart rate